Which term describes lines indicating areas with the same magnetic declination?

Which term describes lines indicating areas with the same magnetic declination?

• A. Agonic Lines.
• B. Groundspeed.
• C. Isogonic Lines.
• D. VOR.

Answer: (C)

Magnetic declination varies by location, so a map marks lines that connect places with the same value. Those lines are isogonic lines. They show where the same compass correction would be needed to align a heading with true north, since the magnetic variation is the same along each line. A special case is the agonic line, where the declination is zero and the compass points directly to true north. The other terms don’t describe lines of equal magnetic declination—groundspeed is speed over the ground, and VOR is a type of navigation beacon.

Magnetic declination varies by location, so a map marks lines that connect places with the same value. Those lines are isogonic lines. They show where the same compass correction would be needed to align a heading with true north, since the magnetic variation is the same along each line. A special case is the agonic line, where the declination is zero and the compass points directly to true north. The other terms don’t describe lines of equal magnetic declination—groundspeed is speed over the ground, and VOR is a type of navigation beacon.